1. Field of the Invention
The present invention relates to an ink jet recording apparatus which uses an ink jet head. More particularly, the invention relates to an exhaust ink processing.
2. Related Background Art
The recording apparatus for recording on a sheet, an OHP sheet, or other recording media has been in practice in a mode in which to install a recording head of various recording methods. For a recording head, there are available a wire dot method, a thermo-sensitive method, a thermal transfer method, and an ink jet method among others. Since the ink jet method is to discharge ink directly onto a recording medium, a particular attention is given as a quiet recording method which is executable at a low running cost.
For the above-mentioned ink jet recording apparatus, a discharge recovery process is usually performed in order to maintain its ink discharge from the recording head in a good condition.
As an example of the discharge recovery process, there is a process (preliminary discharge) for removing the air bubbles and dust particles, which will cause defective discharges to take place or cause ink to become overly viscous and no longer suitable for recording, by providing a cap capable of abutting on and retracting from the discharging port formation surface of the recording head; by allowing the cap to face the discharging port formation surface of the recording head; and by driving the energy generating elements arranged in the nozzles of the recording head for discharging ink in order to discharge ink from the entire discharging ports. Aside from the foregoing preliminary discharge, there is also a process for removing the causes of defective discharge by the application of a forcible suction of ink from the entire discharging ports to exhaust it by use of a suction pump while the discharging port formation surface is covered with the cap.
The ink which is exhausted by the preliminary discharge to the cap is removed from the cap by means of a suction pump.
The ink exhausted from the recording head by the execution of the discharge recovery process such as the forcible suction, preliminary discharge, or the like is conducted by means of the suction pump for storage to an ink retaining member which is connected to the pump. The size or the ink storage capacity of the ink retaining member is regulated by the size of a recording apparatus, the size of an information processing apparatus incorporated in the recording apparatus, and others. Also, in order to store ink efficiently, a part of the ink retaining member is conductively connected to the atmosphere, among some other means, so that the ink is being dried and evaporated while in storage.
Nevertheless, if the ink should flow into the ink retaining member in an amount beyond such a regulated capacity of storage, there might be some cases that the ink intended for storage leaks from the ink retaining member. In general, ink often contains water and some other conductive substances, then the ink which leaks may lead to an accident. Therefore, a sufficient preventive measure should be taken against any leakage of ink.
As an example of the preventive measures, there is devised a method wherein the execution numbers of the suction pump connected to the aforesaid ink retaining member are counted; the stored amount of ink in the ink retaining member is calculated by multiplying the ink inflow to the ink retaining member per execution of the suction pump by the numbers obtained as a result of the aforesaid counting; and a warning is issued to the operator of the recording apparatus when the in-flow of ink reaches the regulated amount of storage.
On the other hand, in a recording apparatus using the recording head which is integrally formed by a recording head and an ink tank, which is arranged to be replaceable in the recording apparatus or a recording apparatus using the recording head and ink tank which are arranged to be individually replaceable for a carriage, the operator executes recording while replacing the recording heads and ink tanks which are provided particularly for the use of different colors of ink. A structure of the kind with which a color printing is easily executable is also in practical use recently.
In a recording apparatus having such a structure as above, there is a possibility that the ink which adheres to the cap is mixed with ink to be used for a color printing because the cap and others, which are the same as those usually used for the conventional head for black ink, abut upon the discharging port formation surface of the recording head for the ink of difference colors. Particularly when the ink remains in the cap in a considerable amount due to the discharge recovery process, the probability for ink mixture is obviously high.
As a measure to prevent this kind of defectiveness from taking place, there has been devised a method wherein before any recording head for color use is installed, the suction pump connected to the cap is actuated for the removal of the ink in the cap while no recording head is mounted, and then, after the ink in the cap is removed, the recording head for color use is installed or a method wherein after the completion of a series of recording operations, the operator is requested to remove the ink in the cap by actuating the suction pump while the cap is kept in a position where it does not abut upon the discharging port formation surface, or an arrangement is made to execute this type of operation automatically.
However, the following problems are encountered in the above-mentioned conventional preventive measures:
When the storage in the ink retaining member is obtained by counting the execution numbers of the suction pump which enables ink to flow into the ink retaining member, the amount of ink sucked from the recording head per suction operation is measured in advance in a state that the cap and the discharging port formation surface of the recording head abut upon each other, and then, the amount of the ink storage is obtained by multiplying the ink amount per suction by the total number of the suction operations.
In the case of this method, however, errors tend to occur between the amount of the ink storage thus calculated and the actual amount of ink storage. As a result, a warning is often given earlier despite the fact that there is still a good room for ink storage.
The major cause of a problem of the kind is that when the suction operation is executed in a state that the cap does not abut upon the discharging port formation surface of the recording head as in the case of mounting the recording head for color use, that is, the event that the suction operation is executed in a state which does not allow any ink to be exhausted by the suction operation, the ink in-flow to the ink retaining member becomes extremely small or "zero" as compared with the case that the suction is executed while the cap and recording head abut upon each other.
Further, the amount of ink which is exhausted by the preliminary discharge into the cap which serves as an ink receptacle for the above-mentioned discharge recovery is "zero" when no recording head is installed.
Also, when using a recording head whose characteristic properties regarding the amount of exhaust ink are different, there are some cases that the amount of ink storage cannot be calculated exactly. As an example, if the ink used by a recording apparatus is different in its viscosity, the amount of ink discharged by the above-mentioned preliminary discharge also differs, and further, it may affect the amount of exhausted ink by the above-mentioned suction operation in some cases.
Also, the ink viscosity varies by changes in the ambient temperature and others, thus varying the amount of exhausted ink from the recording head. As a result, it becomes impossible to measure the amount of ink storage exactly.
Also, when a warning is given regarding the amount of the ink storage in the ink retaining member, it is necessary to replace the ink retaining members. Therefore, a warning of the kind must be given more accurately.
If such a warning is not exact, the ink which is liquid may leak from the ink retaining member, leading to the malfunction of the recording apparatus and the contamination in it. There is also a danger that the ink which has leaked is ignited.
Also, when the amount of exhaust ink to be stored in the ink retaining member reaches the regulated storage, it is necessary to replace the ink retaining members.